This type of ring is used in particular in wristwatches, which are known by the name of a “marquise”. The fact that the arms are rigid offers original aesthetic possibilities. In this type of watch, both arms are held by means of a spring that tends to bring them close to each other. The return force of the spring plays an important role. If it is too weak, there is a risk of the watch being lost, by an inadvertent opening of the arms. If it is too strong, it is less easy to remove the watch from the wrist.
French Patent document No. FR 940 506 proposes to overcome this drawback. It relates to a watch that includes:
two rigid bent arms and an articulation connecting them, said arms being mobile facing each other at the first of their two ends,
a head part, mounted so as to pivot on one of the arms, and
a locking portion mounted so as to pivot on the other arm and co-operating with the head part to define a position in which the head part and locking portion are locked.
With such a solution, the risk of inadvertent unlocking is not negligible, by the locking portion becoming caught for example. Moreover, the large number of articulations can cause the appearance of shake that can affect the comfort and even the security of the wearer. More precisely, according to the invention, the ring is of the type intended to be arranged on a wearer's body part and it includes:                two rigid bent arms and an articulation connecting them, said arms being mobile facing each other at the first of their two ends,        a head part arranged in proximity to the articulation and arranged so as to be able to occupy a first position, called the locking position, and a second position, called the unlocking position, and        first and second connecting means for securing the head part respectively to the first and second arms, said means both being locked when the head part is in the locking position and at least the first of said means being disengaged when the head part is in the unlocked positionThe arms are arranged to occupy:        an open position in which their second ends are separated, such that the ring can be slipped onto or off the wearer's body part through the gap that separates them, and        a closed position in which this gap is reduced, the arms surrounding the wearer's body part.        